In order to prevent the ink nozzles from clogging due to increased ink viscosity in the ink nozzles, the ink nozzle surface in which the ink nozzles are formed is covered with a cap while the inkjet head is in the standby position to prevent the evaporation of moisture from the ink nozzles. Flushing, in which the ink nozzle surface is positioned opposite the cap and ink is discharged from the ink nozzles into the cap, is also performed regularly to prevent clogging. In addition, when an ink nozzle becomes clogged, the ink nozzle surface is covered with the cap, negative pressure is produced by a suction pump in the closed space formed by the nozzle surface and the cap to forcibly expel ink from the ink nozzle into the cap in an ink suction operation that eliminates the clogging. The ink that is expelled from the ink nozzles in the flushing operation and the ink suction operation is absorbed by an ink absorber such as a felt sponge held inside the cap.
The ink discharged from the ink nozzles contains a moisture retention agent such as glycerine, and the moisture retention agent accumulates in the ink absorber as the flushing operation and suction operation are performed. Because the cap does not cover the ink nozzle surface and is open while the inkjet head is printing, moisture evaporates from the ink absorber and the balance between moisture and the moisture retention agent in the cap is lost. Ink nozzle clogging occurs more easily when this balance between the moisture and the moisture retention agent is disrupted because the moisture retention agent attracts moisture from the closed space formed by the cap and the ink nozzle surface when the cap covers the ink nozzle surface, thus accelerating the evaporation of moisture from the ink nozzles and helping to increase the ink viscosity. An inkjet printer that has a cap sealing member, which has a liquid nozzle surface in which liquid nozzles that eject a moisturizing liquid are formed, and supplies moisture into the cap by discharging moisturizing liquid from the liquid nozzles into the cap while the cap is covered by the liquid nozzle surface of the cap sealing member, is described in Patent Literature 1.